From: Aditya Mahajan <adityam@...>
Date: 2006-05-07T13:36:05+09:00
Subject: Output redirection in windows

I am using the one-click installer on windows (RC2). I can not get
output redirection to work with Kernel.system. Consider the following code

F:\tmp\cont-test\test>cat test.rb
def test(command)
   puts command
   puts Kernel.system(command)
   puts "---------------------------"
end

test("mpto mp-test-01.mp")
test("mpto mp-test-01.mp > mp-test-01-test.tex")


mpto.exe is a helper program that comes with metapost and is part of most tex 
distributions. It is included in my path environment. I have a file 
mp-test-01.mp in the current directory. mpto scans the .mp file and outputs on 
stdout. I want to redirect that output to a file. But > does not work.

Running this program gives

F:\tmp\cont-test\test>ruby test.rb
mpto mp-test-01.mp
\gdef\mpxshipout{\shipout\hbox\bgroup
   \setbox0=\hbox\bgroup}
\gdef\stopmpxshipout{\egroup  \dimen0=\ht0 \advance\dimen0\dp0
   \dimen1=\ht0 \dimen2=\dp0
   \setbox0=\hbox\bgroup
     \box0
     \ifnum\dimen0>0 \vrule width1sp height\dimen1 depth\dimen2
     \else \vrule width1sp height1sp depth0sp\relax
     \fi\egroup
   \ht0=0pt \dp0=0pt \box0 \egroup}
\mpxshipout% line 2 mp-test-01.mp
This is a test\stopmpxshipout
\end{document}
true
---------------------------
mpto mp-test-01.mp > mp-test-01-test.tex
false
---------------------------

system "mpto ..." executes correctly (the true after \end{document})
while system "mpto ... > ...." fails. No mp-test-01-test.tex file is created.

When I give the same commands from cmd.exe they work. I am confused why 
something as simple as output redirection is not working. What is the correct 
way to do this?

Thanks,
Aditya